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| NET Audio Full Products Sonance DAC NA200 Power Amplifier Window Passive Preamp CD Player Upgrades
CD Player Clock Upgrades Quad 33 Upgrades Quad 303 Upgrades Accessories
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Quad 405 Full UpgradeA full upgrade can be applied to the 405 which surpasses the standard upgrading of the amplifier circuit boards. The NET Audio Dual Mono Power Supply is fitted to get the best results from each amplifier board by increasing each channels available power reserves and electrically isolating each channels power rails for improved imaging, clarity and bass response. The signal being fed to the amplifier boards should also be as clean as possible as any corruption here cannot be removed by clever amplifier design. Inside the standard 405 the input signal wire run in the wiring loom next to the mains, speaker and transformer wiring which is inevitably going to add electrically induced noise to the input signal wiring. This source of interference can be removed by adding gold plated phono sockets on the chassis next to each amplifier board providing a shorter signal path from socket to board using higher quality silver plated PTFE insulated stranded wire which is now no longer in the wiring loom and is physically far enough from any signal carrying conductors to reduce this interference to a minimum. The short signal path and quality of wire also increases the transparency of the amplifier by reducing any signal degradation as it passes from the input sockets to the amplifier boards. The Quad Current Dumping circuit relies on a bridge for the feedback and for correct functioning, the accuracy of this bridge determining the accuracy of the amplifier to a large extent. Part of the modification process is to use hand selected parts to ensure the bridge is as balanced as possible which lowers distortion and improves clarity. A new high power 9 amp output indictor is fitted to prevent saturation of this component which would unbalance the bridge during music playback and create audible distortion. No matter how low in distortion the class A amplifier is which drives the output and the dumpers, if the output bridge is not balanced then gross distortion will occur directly proportional to the bridge imbalance so these components used in the NET Audio Quad 405 upgrade are carefully matched to ensure peak performance. Once the signal has been amplified, it is now time for it to be passed to the speaker cables. This connection between the amplifier and the speaker cable is important as it is of complex nature. The signals are mixed between high current bass signals and low current treble signals which can quite easily be damaged if this connection is not electrically perfect. Good quality binding posts or banana sockets are what is required so that quality wires can be fitted to carry the signals to your speakers. Additional improvements can be made by replacing the output
transistors with more rugged higher quality output devices such as
the The full upgrade includes a full chassis rewire including the speaker, power supply lines and mains wiring with high quality PTFE insulated Silver plated stranded copper wire and fitting of all new connectors for the input and speaker cable. Quad 405 Full Upgrade includes:-
Optional opamp replacement with OPA627AP devices - probably the best there is. It is best to solder these devices directly to the 405 circuit board but if you require then in sockets please ask when ordering. Opamp replacement consists of
Additionally the 4 output and 4 driver transistors can be upgraded for further sonic improvements. Output stage upgrade includes:-
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